The present invention relates to the field of medical devices and in particular, although not exclusively, to medical cauterization and cutting devices. The invention also relates to drive circuits and methods for driving such medical devices.
Many surgical procedures require cutting or ligating blood vessels or other internal tissue. Many surgical procedures are performed using minimally invasive techniques, a hand-held cauterization device is used by the surgeon to perform the cutting or ligating. The existing hand-held cauterization devices require a desk top power supply and control electronics that are connected to the device through an electrical supply line. FIG. 10 illustrates such an existing hand-held cauterization device currently in use.
It has been known for a number of years that these existing devices are cumbersome and difficult to use during a surgical operation due to the large size of the supply and control electronics and due to the tethering of the hand-held cauterization device to the supply and control electronics. It has also been known for a number of years that these problems would be overcome by providing a battery powered hand-held cauterization device in which the power and control electronics are mounted within the device itself, such as within the handle of the device. However, it is not a simple matter of miniaturising the electronics. The power that has to be supplied to the device during the surgical procedure and the current design of the electronics is such that large capacitors, inductors and transformers as well as heat sinks and fans are required. FIG. 11 illustrates in more detail the different parts of the supply and control electronics that are used in the existing design as illustrated in FIG. 10. Whilst it is possible to reduce the size of the sensing and control electronics, other parts of the circuitry cannot be miniaturised in this way.
In particular, the existing electronics design uses circuitry for providing an adjustable 24 Volt power supply; FETs and associated drive circuitry; a transformer for increasing the supply voltage; and filtering circuitry to remove harmonics from the square wave voltage levels that are generated by the FEE switches and the transformer. Given the voltage levels and the power levels used to drive the cauterization device, the transformers and output filters all have to be relatively bulky devices and large heat sinks and a fan are required to cool the FET switches.
The present invention aims to provide an alternative circuit design that will allow the miniaturisation of the circuitry so that it can be built into the hand-held cauterization device, whilst still being able to provide the power and control required for the medical procedure.